Not in its history has McCoy Stadium seen a starting rotation as good as the one Triple-A Pawtucket ran out to the mound during the first half of this season.

Not in its history has McCoy Stadium seen a starting rotation as good as the one Triple-A Pawtucket ran out to the mound during the first half of this season.

And that rotation might be about to get better.

The best pitching prospect in the Red Sox organization might be lefty Henry Owens, who will turn 22 on Tuesday — just nine days after he started the Futures Game for the United States team at Target Field. He has a 2.12 ERA with 111 strikeouts in 105 2/3 innings at Double-A Portland, dating back to August. He’s even gotten his walk rate under control, having issued just 13 in his last 55 1/3 innings. There’s nothing left for him to prove at Double-A.

Owens and switch-hitting catcher Blake Swihart are the best two players remaining from what was a prospect-studded Portland team at the start of the season. Slugging first baseman Travis Shaw has hit seven home runs since he joined the PawSox in late May. Slick-fielding shortstop Deven Marrero has hit .326 with a .356 on-base percentage in the two weeks since his promotion.

Shaw and Marrero joined the sweet-swinging Garin Cecchini, who has scuffled through June and July but maintained his confidence that his swing is coming around, as prospects who will play every day for the PawSox in the second half. Swihart figures to be up before too long as well, replacing the departed Christian Vazquez.

But the Pawtucket pitching staff remains the marquee attraction.

The PawSox have not yet announced their starting rotation for the second half of the season, which begins Thursday at McCoy Stadium against the Buffalo Bisons. There are too many balls still in the air — including Jake Peavy, who’s lined up to pitch for the Red Sox on Tuesday. If Peavy is traded between now and then, Brandon Workman will take his spot in the Boston rotation. If not, Workman will continue to take his turn with the PawSox.

Of the five starters left who have made at least eight starts for the PawSox this season, four have an ERA under 3.50. Anthony Ranaudo has a 2.62 ERA with 91 strikeouts in 106 2/3 innings. Hard-throwing sinkerballer Allen Webster has a 3.05 ERA in 115 innings. Knuckleballer Steven Wright has a 2.04 ERA in 53 innings since he returned in May from offseason hernia surgery.

And while lefty Chris Hernandez isn’t as a highly touted a prospect, he has a 3.46 ERA while bouncing between the rotation and the bullpen. In 10 starts, his ERA is an even 3.00.

The only PawSox starter to underachieve has been Matt Barnes, who missed the first three weeks of the season while building strength in his shoulder. Barnes has a 5.06 ERA with 57 strikeouts and 31 walks in 74 2/3 innings since his arrival in late April.

Barnes’ season has something of a Ranaudo-in-2012 vibe to it. Ranaudo compiled a 6.69 ERA in nine starts at Double-A Portland that year while dealing with a groin injury and its ensuing complications. The following year, however, he posted a sub-3.00 ERA in 19 starts with the Sea Dogs and earned a summons to Triple-A.